Don't IM meth, even if it was 100% pure, methamphetamine is extremely caustic.
Yes IVing methamphetamine has a rush, a very intense one too. The first time I shot meth in my teens I was with an older fella who put about 100 mgs of extremely pure product in my spoon. He said " oh it doesn't have much of a rush compared to Coke, at least not to me" so I shoot this hit and get hit with one of the most intense rushes I have experienced even still to this very day.i wanted to be angry that he misled me but I was in bliss ha.
I personally don't smoke it, I find I use more product to get less high then if I were to sniff or shoot it. I don't think I have a shitty technique and I get ice of food quality for sure.
If ur dead set on IVing meth, I'd say start with 50-75 mgs to gauge the effects etc. If it's good dope that's all u should need. I know what I get I can get 2 shots from a point ( I typically will shoot about 70 mgs of shard and get a good rush, and redose the other 30 mgs a little after to keep the stimulation going)